CN111337798A - Insulation monitoring and partial discharge fault diagnosis method for extra-high voltage converter transformer - Google Patents
Insulation monitoring and partial discharge fault diagnosis method for extra-high voltage converter transformer Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
Abstract
An ultra-high voltage converter transformer insulation monitoring and partial discharge fault diagnosis method includes the steps that 1 group of ultra-high frequency couplers (UHF) are arranged in each of the XYZ directions of a converter transformer body to collect partial discharge signals, an empirical mode decomposition algorithm is utilized, HHT band-pass filtering is conducted to obtain a signal time-frequency matrix A, and then multi-dimensional energy parameters of the signals are obtained through calculationAnd a multidimensional sample entropy parameter P ═ P1,p2,…,pl]And establishing a characteristic plane by the parameters, and finally identifying and classifying the characteristics by using a support vector machine algorithm based on a hypersphere to realize insulation monitoring and fault diagnosis of the converter transformer.
Description
Technical Field
The invention relates to the field of insulation monitoring and partial discharge fault diagnosis of large-scale power equipment such as a converter transformer, a conventional transformer and the like, in particular to an insulation monitoring and partial discharge fault diagnosis method for an extra-high voltage converter transformer.
Background
Partial discharge is both a precursor sign of insulation degradation of a power transformer and a major cause of degradation of insulation performance of the power transformer. At present, most of means and measures for transformer insulation monitoring and partial discharge fault diagnosis are offline detection and analysis, an effective fault signal extraction method and a fault diagnosis method are lacked, and the insulation and partial discharge faults of a large power transformer are difficult to monitor and diagnose online.
Chinese patent documents: "large transformer partial discharge positioning detection method" (CN 201910347315.6): four ultrasonic sensors are arranged on the surfaces of a transformer bushing and a transformer oil tank, acquired ultrasonic waveforms are analyzed to obtain positioning parameters and time delay, and then a time difference positioning equation is used for solving to obtain the position of a local discharge source. And finally, repeating the test to obtain an average value, and obtaining the accurate position of the partial discharge. The patent belongs to an on-line monitoring and diagnosis method of a transformer, however, the method analyzes and processes a received discharge ultrasonic signal, obtains local discharge source coordinates (x, y, z) by solving a time difference positioning equation, and finally solves an average value after repeating up to hundreds of tests to obtain the local discharge source coordinates of hundreds of tests. The method depends on the ultrasonic sensor, and the final local discharge source coordinate can be obtained only by repeated tests.
Disclosure of Invention
The invention aims to provide an insulation monitoring and partial discharge fault diagnosis method for an extra-high voltage converter transformer, which aims to accurately detect and extract the characteristic information of a partial discharge signal, find out the characteristic parameters of different faults by analyzing signal energy values and sample entropies on different frequency bands, realize the diagnosis and identification of the different faults and monitor and master the insulation degradation degree of the converter transformer.
1. The purpose of the invention is realized as follows: an insulation monitoring and partial discharge fault diagnosis method for an extra-high voltage converter transformer is characterized by comprising the following steps:
1) respectively arranging a set of the ultrahigh frequency coupler in XYZ directions of a transformer body to be monitored, wherein the ultrahigh frequency coupler acquires an original partial discharge signal x (t) of a converter transformer by using the ultrahigh frequency coupler, the sampling frequency of the ultrahigh frequency coupler is f, the number of sampling points is n, and m intrinsic mode functions IMF components are obtained after EMD decomposition;
2) obtaining the time frequency distribution spectrum of each IMF component through Hilbert transform, dividing the IMF component into l frequency bands, performing HHT band-pass filtering, reconstructing to obtain components of a signal x (t) on different frequency bands, and obtaining a signal x (t) time frequency matrix A
Wherein, aijData representing the signal x (t) in each frequency band, i 1.. and l, j 1.. and n;
3) calculating each row of the time-frequency matrix a, that is, each frequency band, according to equation (2), to obtain an energy value e (i) of the signal x (t) in the frequency band, i ═ 1.. multidot.l; the normalization process is performed according to equation (3), and the energy parameters of the signals x (t) in the l frequency bands are recorded as: e ═ E*(1),E*(2),…,E*(l)];
4) Calculating each row of the time-frequency matrix a, that is, each frequency band according to equation (4), to obtain a sample entropy p (i) of the signal x (t) in the frequency band, i ═ 1.. multidot.l; the sample entropy values over the l frequency bands from which the PD signal is derived are then recorded as: p ═ P (1), P (2), …, P (l);
typically, r is 0.1-0.25 times the standard deviation of the time series of signal x (t), and m is an integer from 30 to 50;
5) establishing a characteristic plane by using the energy parameter and the sample entropy parameter of the PD signal, and recording the energy parameter E (i) and the sample entropy parameter p (i) on the same frequency band as a characteristic point siAs a result, the set S of all feature points of the PD signal on the feature plane is:
S={(E(1),P(1)),(E(2),P(2)),···,(E(l),P(l))}。
on the characteristic plane of the PD signal, there is a small sphere (a)m,Rm) Contain almost all characteristic points of the same type of fault, which are recorded as:
wherein a ismRepresents the center of sphere, RmRepresents the square of the radius of the sphere and,is a relaxation variable, and m is the dimension of the hypersphere;
recording the sample of the fault signal to be diagnosed as X ═ X1,x2,···,xlIn which xiI 1,2, represents a feature point in the sample; if the sample X belongs to which class, firstly, the square sum of the distances from all points in the sample X to each sphere center is calculatedAnd is reacted with l.RmMaking a comparison, let d representThe number of (2);
(1) when d is 0, the majority of feature points of the sample X are positioned at the periphery of all the spheres, and a sphere closest to the area of the sample X needs to be found if d is 0Then sample X belongs to class p;
(2) when d is 1, the sample X belongs to the class represented by the sphere;
(3) when d is larger than 1, the characteristic point of the sample X is positioned in the area where the plurality of spheres intersect;
step 1: recording the classification serial numbers of all balls containing the sample X as a set I;
Step2:respectively calculateAndin thatProjection a ontoiD and aiC; wherein All represent a spatial vector;
step 3: comparison aiD and aiC, if the projection a of most of the characteristic points X of the sample XiD is less than aiC, the sample X belongs to the category i, otherwise the sample X belongs to the category j;
step4, let set I be It-1And returning to the step2 until only one element is contained in the set I, namely the sample X belongs to the class represented by the element.
The signal sample entropy calculation process is as follows:
for each row a of the time-frequency matrix Ai1,ai2,…,ainThe following processing is carried out, and the sample entropy is calculated, and the steps are as follows:
step 1: determining a mode dimension m and a threshold value r, and recording data of one row of the matrix A as: x is the number of1,x2,…,xn(ii) a And converts it into a set of m-dimensional vectors,
X(i)=[x(i) x(i+1) … x(i+m-1)]
wherein i is 1,2, …, n-m +1
Step 2: redefining the distance formula between X (i) and X (j)
Step 3: and counting the template matching number N of d (i, j) < r for each value of i, wherein the ratio of the template matching number N to the total number N-m +1 is:
wherein j is more than or equal to 1 and less than or equal to n-m, and j is not equal to i
Step4: calculate the average of all i values
Step 5: repeating Step 1-Step 4 according to the mode dimension m +1 to obtain Bm+1(r); calculate the sample entropy of this row of data for matrix A
Step 6: and repeating Step 1-Step 5 for other rows of data of the matrix A to respectively obtain sample entropy values of the PD signal on l frequency bands.
The invention has the beneficial effects that:
the invention describes the fault characteristics of the partial discharge signal by establishing a description method of the partial discharge signal characteristics with multi-dimensional energy parameters and multi-dimensional sample entropy parameters as main characteristics, and then identifies and diagnoses the fault characteristics by the partial discharge fault diagnosis method based on the hypersphere support vector machine. By the method, the characteristic information of the partial discharge signal can be accurately detected and extracted, and the insulation degradation degree of the converter transformer can be monitored and mastered.
Drawings
FIG. 1 is a schematic drawing of a characteristic plan of a PD signal
FIG. 2 is a schematic diagram of a method for determining intersection region
FIG. 3 is the EMD algorithm flow
Detailed Description
Referring to fig. 1, 1 set of ultrahigh frequency couplers (UHF) are arranged in each of XYZ directions of a converter transformer body to collect Partial Discharge (PD) signals x (t), an empirical mode decomposition algorithm (EMD) is used to decompose the signals x (t) into m narrowband components, Hilbert transform is used to obtain a time-frequency distribution spectrum of each component, HHT band-pass filtering is performed, components of the signals x (t) on different frequency bands are reconstructed, and a time-frequency matrix a of the signals x (t) is obtained. Calculating to obtain the multi-dimensional energy parameter of the signal according to the formulas (3) and (4)And a multidimensional sample entropy parameter P ═ P1,p2,…,pl]. Establishing a feature plane (see fig. 2) by using multi-dimensional energy parameters and multi-dimensional sample entropy parameters, and recording energy parameters E (k) and sample entropy parameters p (k) on the same frequency band as a feature point sk(e (k), p (k)), and finally using hypersphere-based supportThe measuring machine algorithm identifies and classifies the characteristics of the transformer, and realizes insulation monitoring and fault diagnosis of the transformer.
A description method of partial discharge signal characteristics with multi-dimensional energy parameters and multi-dimensional sample entropy parameters as main characteristics,
1) respectively arranging a set of the ultrahigh frequency coupler in XYZ directions of a transformer body to be monitored, wherein the ultrahigh frequency coupler acquires an original partial discharge signal x (t) of a converter transformer by using the ultrahigh frequency coupler, the sampling frequency of the ultrahigh frequency coupler is f, the number of sampling points is n, and m intrinsic mode functions IMF components are obtained after EMD decomposition;
2) obtaining the time frequency distribution spectrum of each IMF component through Hilbert transform, dividing the IMF component into l frequency bands, performing HHT band-pass filtering, reconstructing to obtain components of a signal x (t) on different frequency bands, and obtaining a signal x (t) time frequency matrix A
Wherein, aijData representing the signal x (t) in each frequency band, i 1.. and l, j 1.. and n;
3) calculating each row of the time-frequency matrix a, that is, each frequency band, according to equation (2), to obtain an energy value e (i) of the signal x (t) in the frequency band, i ═ 1.. multidot.l; the normalization process is performed according to equation (3), and the energy parameters of the signals x (t) in the l frequency bands are recorded as: e ═ E*(1),E*(2),…,E*(l)];
4) Calculating each row of the time-frequency matrix a, that is, each frequency band according to equation (4), to obtain a sample entropy p (i) of the signal x (t) in the frequency band, i ═ 1.. multidot.l; the sample entropy values over the l frequency bands from which the PD signal is derived are then recorded as: p ═ P (1), P (2), …, P (l);
typically, r is 0.1-0.25 times the standard deviation of the time series of signal x (t), and m is an integer from 30 to 50;
5) establishing a characteristic plane by using the energy parameter and the sample entropy parameter of the PD signal, and recording the energy parameter E (i) and the sample entropy parameter p (i) on the same frequency band as a characteristic point siAs a result, the set S of all feature points of the PD signal on the feature plane is:
S={(E(1),P(1)),(E(2),P(2)),···,(E(l),P(l))}。
a partial discharge fault diagnosis method based on a hypersphere support vector machine comprises the following steps:
on the characteristic plane of the PD signal, there is a small sphere (a)m,Rm) Contain almost all characteristic points of the same type of fault, which are recorded as:
wherein a ismRepresents the center of sphere, RmRepresents the square of the radius of the sphere and,is a relaxation variable, and m is the dimension of the hypersphere;
recording the sample of the fault signal to be diagnosed as X ═ X1,x2,···,xlIn which xiI 1,2, represents a feature point in the sample; if the sample X belongs to which class, firstly, the square sum of the distances from all points in the sample X to each sphere center is calculatedAnd is reacted with l.RmMaking a comparison, let d representThe number of (2);
(1) when d is 0, the majority of feature points of the sample X are positioned at the periphery of all the spheres, and a sphere closest to the area of the sample X needs to be found if d is 0Then sample X belongs to class p;
(2) when d is 1, the sample X belongs to the class represented by the sphere;
(3) when d is larger than 1, the characteristic point of the sample X is positioned in the area where the plurality of spheres intersect;
step 1: recording the classification serial numbers of all balls containing the sample X as a set I;
Step 3: comparison aiD and aiC, if the projection a of most of the characteristic points X of the sample XiD is less than aiC, the sample X belongs to the category i, otherwise the sample X belongs to the category j;
step4, let set I be It-1And returning to the step2 until only one element is contained in the set I, namely the sample X belongs to the class represented by the element.
The signal sample entropy calculation process is as follows:
for each row a of the time-frequency matrix Ai1,ai2,…,ainThe following processing is carried out, and the sample entropy is calculated, and the steps are as follows:
step 1: determining a mode dimension m and a threshold value r, and recording data of one row of the matrix A as: x is the number of1,x2,…,xn(ii) a And converts it into a set of m-dimensional vectors,
X(i)=[x(i) x(i+1) … x(i+m-1)]
wherein i is 1,2, …, n-m + 1
Step 2: redefining the distance formula between X (i) and X (j)
Step 3: and counting the template matching number N of d (i, j) < r for each value of i, wherein the ratio of the template matching number N to the total number N-m +1 is:
wherein j is more than or equal to 1 and less than or equal to n-m, and j is not equal to i
Step4: calculate the average of all i values
Step 5: repeating Step 1-Step 4 according to the mode dimension m +1 to obtain Bm+1(r); calculate the sample entropy of this row of data for matrix a:
step 6: and repeating Step 1-Step 5 for other rows of data of the matrix A to respectively obtain sample entropy values of the PD signal on l frequency bands.
Claims (3)
1. The method for insulation monitoring and partial discharge fault diagnosis of the extra-high voltage converter transformer is characterized in that hidden data information of a fault sample is utilized to the greatest extent, characteristic parameters of different faults are found out by analyzing signal energy values and sample entropies on different frequency bands, and different fault diagnosis and identification are realized, and the specific process is as follows:
1) respectively arranging a set of ultrahigh frequency couplers in XYZ directions of a transformer body to be monitored, acquiring an original partial discharge signal x (t) of a converter transformer by using the ultrahigh frequency couplers, wherein the sampling frequency is f, the number of sampling points is n, and obtaining m intrinsic mode functions IMF components after EMD decomposition;
2) obtaining the time frequency distribution spectrum of each IMF component through Hilbert transform, dividing the IMF component into l frequency bands, performing HHT band-pass filtering, reconstructing to obtain components of a signal x (t) on different frequency bands, and obtaining a signal x (t) time frequency matrix A
Wherein, aijData representing the signal x (t) in each frequency band, i 1.. and l, j 1.. and n;
3) calculating each row of the time-frequency matrix a, that is, each frequency band, according to equation (2), to obtain an energy value e (i) of the signal x (t) in the frequency band, i ═ 1.. multidot.l; the normalization process is performed according to equation (3), and the energy parameters of the signals x (t) in the l frequency bands are recorded as: e ═ E*(1),E*(2),…,E*(l)];
4) Calculating each row of the time-frequency matrix a, that is, each frequency band according to equation (4), to obtain a sample entropy p (i) of the signal x (t) in the frequency band, where i is 1.. and l; the sample entropy values over the l frequency bands from which the PD signal is derived are then recorded as: p ═ P (1), P (2), …, P (l);
usually, r is 0.1-0.25 times of the standard deviation of the time sequence of the signal x (t), m is an integer of 30-50, and n is the number of sample sampling points;
5) establishing a characteristic plane by using an energy parameter and a sample entropy parameter of the PD signal, and converting energy on the same frequency bandThe parameter E (i) and the sample entropy parameter p (i) are denoted as a feature point siAs a result, the set S of all feature points of the PD signal on the feature plane is:
S={(E(1),P(1)),(E(2),P(2)),···,(E(l),P(l))}。
2. the partial discharge fault diagnosis method according to claim 1, characterized in that: on the characteristic plane of the PD signal, there is a small sphere (a)m,Rm) Contain almost all characteristic points of the same type of fault, which are recorded as:
wherein a ismRepresents the center of sphere, RmRepresents the square of the radius of the sphere and,is a relaxation variable, m is the dimension of the hypersphere,representing a feature point;
recording the sample of the fault signal to be diagnosed as X ═ X1,x2,···,xlIn which xiI 1,2, represents a feature point in the sample; if the sample X belongs to which class, firstly, the square sum of the distances from all points in the sample X to each sphere center is calculatedAnd is reacted with l.RmMaking a comparison, let d representThe number of (2);
(1) when d is 0, the majority of feature points of the sample X are positioned at the periphery of all the spheres, and a sphere closest to the area of the sample X needs to be found if d is 0Then sample X belongs to class p;
(2) when d is 1, the sample X belongs to the class represented by the sphere;
(3) when d is larger than 1, the characteristic point of the sample X is positioned in the area where the plurality of spheres intersect;
step 1: recording the classification serial numbers of all balls containing the sample X as a set I;
Step2:respectively calculateAndin thatProjection a ontoiD and aiC, wherein All represent a spatial vector;
step 3: comparison aiD and aiC, if the projection a of most of the characteristic points X of the sample XiD is less than aiC, the sample X belongs to the category i, otherwise the sample X belongs to the category j;
Step4, let set I ═ It-1And returning to the step2 until only one element is contained in the set I, namely the sample X belongs to the class represented by the element.
3. The partial discharge fault diagnosis method according to claim 2, characterized in that: the signal sample entropy calculation process is as follows:
for each row a of the time-frequency matrix Ai1,ai2,…,ainThe following processing is carried out, and the sample entropy is calculated, and the steps are as follows:
step 1: determining a mode dimension m and a threshold value r, and recording data of one row of the matrix A as: x is the number of1,x2,…,xn(ii) a And converts it into a set of m-dimensional vectors,
X(i)=[x(i)x(i+1)…x(i+m-1)]
wherein i is 1,2, …, n-m +1
Step 2: redefining the distance formula between X (i) and X (j)
k=0,1,…,m-1
Step 3: and counting the template matching number N of d (i, j) < r for each value of i, wherein the ratio of the template matching number N to the total number N-m +1 is:
wherein j is more than or equal to 1 and less than or equal to n-m, and j is not equal to i
Step4: calculate the average of all i values
Step 5: repeating Step 1-Step 4 according to the mode dimension m +1 to obtain Bm+1(r); calculate the sample entropy of this row of data for matrix A
Step 6: and repeating Step 1-Step 5 for other rows of data of the matrix A to respectively obtain sample entropy values of the PD signal on l frequency bands.
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